This application seeks support for four linked research projects focused on the influences of components of the tumor microenvironment on the progression of primary tumors and metastases using both human tumor materials, cell biological methods and genetically engineered mouse models of cancer, with particular emphasis on breast and lung cancer. The microenvironment of tumors contains many non-tumor cells, including macrophages, neutrophils and myofibroblasts and several of the projects use both mouse models and human patient samples to investigate the influences of these cells on the behavior of the tumor cells - both locally derived as well as systemically recruited cells from the bone marrow and elsewhere (e.g., spleen).The generation and trafficking of these cells will be analyzed using sophisticated in vivo imaging methods in both mouse models and human patients. The secreted signals (growth factors and cytokines) that recruit and program these cells of the reactive tumor stroma will be investigated as will be the mechanisms of their effects on the tumor cells - induction of EMT, acquisition of stem-cell-like properties, migration, invasion, intravasation and extravasation and formation of metastases. The reactive stroma also contains a complex extracellular matrix (ECM), which includes bound growth factors and cytokines and the composition of this ECM changes markedly during tumor progression - these changes will be analyzed in detail using newly developed proteomics methods and their functional significance will be analyzed by manipulating the expression of relevant genes in both tumor and stromal cells. The four project leaders have a history of productive interactions and collaborations that will be further enhanced by TMEN support. The combined use of human patient material to anchor the discoveries to clinically correlated criteria and mouse models for investigation of the causality of the identified interactions in pre-clinical tests will allow progess possible with neither system alone. The common goal of these projects will be to dissect the cellular and non-cellular effects of the tumor stroma on tumor progression with a view to identifying novel biomarkers and signatures of diagnostic and prognostic value and new targets for potential therapeutic intervention.